Choice of absorbent-refrigerant mixtures

Twenty-six absorbent—refrigerant combinations, holding good promise as fluid systems, have been considered for single stage absorption air conditioning system. These fluids have been compared on the basis of solution characteristics, life expectancy characteristics and refrigeration cycle characteristics. The mass flow rates of rich and poor solutions per ton of refrigeration capacity and the coefficient of performance (CP) were compared for an evaporator temperature of 5°C, absorber and condenser temperatures of 35°C and a generator temperature of 120°C (low grade energy sources). More than half of the waste energy available in industry happens to be at a temperatures below 200°C. Other types of low grade thermal energy such as solar energy and geothermal energy can be used in operating vapour absorption refrigeration and air-conditioning systems.     

Profit analysis of two-unit standby system with rest period for the operator and correlated failures and repairs

This paper analyses a two-unit cold standby system with the provision of rest for the operator. After working a random amount of time, the operator needs to rest for a random amount of time and during the rest period the system comes down, but does not fail. Also, the failure and repair times of each unit are assumed to be correlated, by taking their joint density as a bivariate exponential. The system is observed at suitable regenerative epochs to obtain various reliability characteristics of interest to system designers as well as operations managers. Numerical results pertaining to a particular case are also presented.     

Towards determining the optimal size of unit irrigation command area

The size of a irrigation unit command area (UCA) has significant influence on distribution of water among farms and the efficiency of irrigation within farms. A model incorporating the concepts of equity, efficiency and productivity is developed for designing optimal UCA size and is validated with data from Bhakra Canal System in India. The design of watercourses by adopting the suggested procedure would lead to improvement in three‐criterion parameters (equity, efficiency and productivity). This establishes the need for and scope of modifying the existing designs.     

Reliability analysis of star type local area networks

The present work studies the reliability of a star type computer networking system, normally used for Local Area Networks (LAN). The regenerative point technique has been used to derive expressions for various reliability characteristics of interest. Numerical computations have also been done to present the results graphically.     

White electroluminescence from stacked organic light emitting diode

Electroluminescent zinc complex [(2-(2-hydroxyphenyl)benzoxazole)(2-methyl-8-hydoxyquinoline)] zinc [Zn(hpb)mq] has been synthesized. It has been used with a blue emitting zinc complex Zn(hpb)₂, to fabricate stacked organic light emitting diode (OLED). Thickness of layers of these materials has been optimized to achieve white light emission. The maximum luminescence of the device was 8390 Cd/m² at 14 V. Commission Internationale de l’Eclairage coordinates of the device, with 40 nm thickness of Zn(hpb)₂ and 15 nm thickness of Zn(hpb)mq, were (0.29, 0.38) at 7 V and were well within the white region. A model has been presented for simulating the electroluminescence (EL) spectrum of stacked OLED based on Gaussian disorder model using Monte-Carlo technique. From the model the energetic disorders, highest ocuppied molecular orbital and lowest unoccupied molecular orbital positions of different emissive layers and the excimer layer have been estimated.     

C–V index of hyperabrupt p-n junctions

C–V index n for hyperabrupt p⁺-n junctions with exponentially retrograded n-region has been computed numerically for different values of parameters characterizing the impurity profile and the results have been plotted graphically. Although n is found to vary with the bias across the junction for any given impurity distribution, the maximum value nmax of n is determined only by the ratio of the background concentration to the crossover concentration in the retrograded region. By making this ratio R₀ smaller and smaller, values of n substantially larger than unity can be obtained. Practical considerations, however, limit the maximum value of n to about 10. An empirical relation expressing nmax as a function of the ratio R₀ has been obtained. Calculated results are compared with the values of n measured on hyperabrupt junctions fabricated by a double diffusion process.     

Changes in electronic and optical characteristics of halogen–alkali adsorbed WSe2 monolayer

Journal of Materials Science: Materials in Electronics - Adsorbing halogen and alkali metals atoms modify the optical and electrical characteristics of WSe2 monolayer (2D). The electrical and...